Transmitter for guided aircraft controls



Oct. 28, i952 P. w. NosKER TRANSMITTER FOR GUIDED AIRCRAFT CONTROLS 7 Sheets-SinaaiI l Original Filed Dec. 11, 1946 Z 3 3 3 7 f f w//f W M E .m 0 E 3 3 l .m 5 0 N m W E W 45. ZZ- f/ 0 aLl. z rl 7 We. 2f- HM, 7. w @E Pt L/L Wl. L L/ 1A E m 2 n /u n A5 ,5 31:42 T I ,.7 al@ .MQW

INVENTOR.

42, BEEF/Vif? Oct. 28, 1952 P. w. NosKER TRANSMITTER FOR GUIDED AIRCRAFT CONTROLS 7 Sheets-Sheet 2 Original Filed Dec. 1l, 1946 .WHY

Oct. 28, 1952 P. w. NosKER TRANSMITTER FOR GUIDED AIRCRAFT CONTROLS 7 Sheets-Sheet 3 Original Filed Dec. 11. 1946 Oct. 28, T952 7 Shams-.Sheet `4:

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TRANSMITTER FOR GUIDED AIRCRAFT@` CONTROLS original Filed pw. 11, 194e v v sheets-suse@ e Oct 28 1952 P. w. NosKER TRANSMITTER FOR GUIDED AIRCRAFT CONTROLS Sheelts-Sheet '7 Original Filed Dec.

Patented Oct. 28, 1952 UNITED? l srarss TRANSMFITER FOR GUIDED AIRCRAFT CONTROLS Paul W. Nosker, Yellow Springs, Ohio 2 claims. (c1. 25o- 12). l (Granted under the act of March 3, 1883, as

amended April 30, 1928; 370 O. -G. 757) The invention described herein maybe manufactured and vused by or for the Government for governmental purposes Without payment to me of any royalty thereon.

This application is a division of application Serial No. 715,595 of Paul W. Nosker filed December 11, 1946 entitled Remote Control System. now Pat. No. 2,515,254 issued July 18, 1950, and is'awcontinuation in part of Noskers pending application Serial No. 494,462 entitled Aerial Torpedo.

This invention relates to a remote control system for aircraft, guided missels andthe like.

In the past, various systems have been used for controlling remotely aircraft Yand the like. It is conventional practice when controlling target aircraft, guided missels, and test aircraft engaged in hazardous missions, to employ an automatic pilot and other automatic devices on the aircraft to maintain preset flight conditions, including predetermined variations of those conditions, such conditions being maintained by the automatic-equipment in -the absence of radio or other controlling signals from remote points. Remote control of such vehicles has been exercised by transmitting and receiving radio signals operating upon variouslelements of the automatic control systems. In the arrangements of the kind just described as belonging to the `present conventional art, it will be observed that the vehicle or aircraft is actually controlled by the automatic mechanisms installed in. it, vand the received A'remote-control signals serve merely to .readjust or to alterlthe manner of response of such automatic control devices. It is correct to say that the so-calle'd remote control systems of this type are really automatic control systems thatare subject to 'resetting by remote control.

Remote control equipment, as at present provided and used, imposes limitations `of major consequence Wherever a high degree of maneu- 'and thereby initiates an operation which continues as long as that particular signal is'transmitted. The extent or distance to which that particular operation progresses depends upon the length of time of 'transmission ofthe particular controlling signal involved.' In conse-y quence, the remote pilot or the operator `in present-day conventional practice manipulates push buttons or switches Which are not similar to conventional airplane controls and further, the remote pilot or operator has no direct control over the motions of the elevator, rudder, or

ailerons on the aircraft. Furthermore, conventional systems have inherent time lags which are highly undesirable when abrupt or extensive maneuvers must be performed.

`The present system of remote control is in#- tended for and is particularly adapted to the flight testing of military aircraft or missels to extreme limits of airspeed, acceleration or other flight parameters.` The present remote control system is intended to be suiciently versatile to permit attainment of every flight condition and attitude of which an airplane or missile is capable. n

In consequence of the fact that these objectives seem to lbe unattainable bythe usual remote control systems or their ordinarymodifications. I have'provided a system which is different from 'the' conventional in the following respects:

4 a. The desired maneuversV of the missile or the like and their manner of execution are less limited by my system ofremote control than by the characteristics of the missile or other aircraft, itself.

q b. The `remote control system which 1 have provided will work Well in any controlled airplane .'or guided missile having airplane-type controls,

.regardless -of the peculiarity of the flight characteristics of that airplane or missile.4

c. The remote control systemis a naturalone inwhich thexremotezpilot or operator performs his usual functions 4in the accustomedv manner.

d. A proportional control systemis incorporated, by whioh received signals establish directly the position of each control element on the controlled aircraft.

e. The total systemA preferably includesy two separate television channels by Whichthehuman pilotln a simulatedcockpit in the remote control lstation receives an image of the forward View from the controlled airplane or missile and an image of an instrument panelvon. the controlled airplane'. In this way, it may: bel said that the remote control pilot actually-nies the aircraft or missile being flown by remote'control on instruments in thesame mannerth'at he would do if he were situatedon that controlled aircraft. It is therefore Apossible to perform 3 safely the first flights of an aircraft under full remote control.

One object of the present invention is to provide a remote control apparatus which is not dependent upon or sensitive to the particular iiying characteristics of the aircraft to be controlled. When such a system is provided, the remote control receiving system can be transferred from one aircraft to another and will function well in any ying vehicle having effective 4controls provided the control limits are rst suitably adjusted. No other adjustment is necessary and neither is preliminary testing required to accommodate the new installation `to the flight characteristics of the particular aircraft involved. l

A second object of the invention is to provide such controlled equipment on the aircraft that it will always be able to cope properly with unusual flight conditions vor situations. In contrast, automatic pilot controls in use at present cannot be relied upon to effect successful recoveryffrom intentional or inadvertent spins.

A third object is to provide a control system which can function throughout a full 360 of either roll or pitch. Present-day gyroscopic automatic pilots 'of the 'attitude or position type are 'unable to function throughout such a complee ,range s A lfourth object isto provide a system in which the positioning of la control on a power-driven controlled aircraft by a signal yreceiving station I nunted thereon is dependent upon Yrelative amplitudes of frequencies of two different signals simliltaneously transmitted `from asignal transmittel' ,Siit .the 'amplitude .ratio 0f the two signals being variable at the will of the operator at the transmitting station.

ln the drawings:

Fig. 1 is a block and schematic diagram 'of a circuit `at 'a 'signal transmitting station;

Fig. 2 is avblo'ck and lschematic diagram 'of a control-operating circuit at Ia signal receiving station for receiving vand operating V'controls in response to ysignals radiated from the signal transmitting station shown in Fig. 1;

'Fig.j3 is a block andschematic diagram of a modifled *circuit for the signal transmitting station; y

Fig. 3a is a plan view of one lforni yof the transfer switch |2I;

Fig. i Ais a block and schematic 'diagram of another embodiment vof a circuit l'for vthe signal receiving station adapted lto he vused 'with the transmitter station circuit which is "shown vin Fig. 3;

Fig. 5 is a lateral velevation .of a servomotor and a :sectional elevation of a gear `train Vhousing showing a-gear train and a position-'selecting po'- tentiometer insecti'on Atherein and a power takeoff disposed "outwardly :of the housing and operated by the gear train;

Fig. 6 is a diagrammatic elevation :of the vvpo'- tentiom-eter shown inFig. 5;

Fig. '1 A`is a 'iblo'ck and schematic diagram Yof another embodiment of the circuit at the signa-l transmitting station with 4setting l'indicating means and with a trim control as parts thereof;

vzlig. 8 visa block and schematic diagram of another embodiment of the receiving station circuit showncin Fig. `2;

Fig. 9 is a block and schematic 'diagram of the circuit of ya transmitter '.station'similar to that shown `in Fig. 1 with the difference that it made tof'ra-diate light waves instead of radio waves;

Fig. 10 is a block and schematic diagram of a control receiving station similar to that shown in Fig. 2 with the difference that it is responsive to light waves instead of to radio waves; and

Fig. 11 is a block and schematic diagram showing the over-all system and the interrelations between the control and controlled stations, especially the relations rof the radiant energy channels to the remote pilot or operator.

In Fig. 11, is the missile, airplane or other control station. 10| is the ground or mobile control station which may be airborne. A television camera 102 is located within the missile',

preferably in the lnose, where it may have a clear view ahead. Its 'output is delivered to a television transmitter 103 from whence it is beamed or broadcast from an antenna '|01 to the control station 10|. A second television camera 104 is disposed to view an instrument board 105, the dials of which show the flight and operating conditions aboard the missile 100. The outputV of camera 104 is delivered to a television transmitter 10E, from whence it is beamed or broadcastfrom an antenna 106a to the control station 10|. A receiving system 108 is provided with an antenna 109 and is connected to actuate the missile flying controls -1II. Y

In the control station 10|, an lantenna 1|2 intercepts signal from the' television transmitter 103 and a second antenna 1|3 intercepts signal from the television transmitter 106. Television receivers 1I4 and 1I5 are connected to antennas 1I2 and 1I3, respectivelyJ and lrinescopesl1|6 and 1I1 are connected respectively to television receivers 1I# and 1I5. VA pilots seat 1|8 is disposed within easily visiblerange of the kinescopes and within conventional distance and position from pedals 1 I 9 and 120 for actuating the rudder.. A conventional control stick 12| is provided -for aileron and elevator functions. Pedals 1I9 and 1'20 and istick 12jl are each connected to a trans'- m-itting lsystem 1'22 Vwhich is arranged lto radiate `signal from antenna 123. The signals shown as being radiated lfrom Vantenna 123 may be either radio or lc )ther radiant lightA Waves. Appropriate receivers in the control station are used `in'each CaSe.

Referring to Fig. -1,a-cont-ro1 station indicated in Fig. 11 as control station 10| is shown and has five signal'generators I2, 13, I4, and I5, 'each l signal generatorV producing electrical impulses Which maybe pure sine waves, these being of constant amplitude and each 'having ay different constant frequency. The outputs of `the signal generators II, I2, I3, and I4 are fed `to variable -attenuatorsor potentiometers I6, I1, I8, and I9,

respectively, land then through ampliers 20. 2|, 22, and 23, whichare respectively connected `in parallel to leads 24 and A25. The output of the signal generator I5 fed through a lfixed attenuator 26 and amplifier 21 to leads 24-and 25. Leads 24 and.,2'5 provide input for a modulator 28 which is connected through leads 29 and 30 to aradio transmitter 3| having the -usual con'- tween the rudderpeda-ls H9 and 120 Vandpotem tiometer I8. Dashed lines 126 represent a mechanical linkage between a throttle control and the potentiometer I9. The relation of these controls to the transmitter is indicated in Fig. 11 with the exception that the throttle control is not shown.

Fig. 2 shows a circuit at the control station or missile indicated as 100 in Fig. 11. Receiving antenna 40 at the control station is coupled to a radio receiver 4I having a ground 42. Receiver 4| is connected by leads 43 and 44 to band pass filters 45, 46, 41, 48, and 49, arranged in parallel. The band pass lters 45 to 49, inclusive, are 4tuned to pass signals of the respective frequencies of the signal generators II to I5, in clusive. Combined signals received by the antenna 40, after demodulation by a receiver 4I, are separated or channeled by the band pass-filters 45 tov 49, inclusive, and are then amplified by amplifiers 50, 5|, 52, 53, and 54, respectively, which are connected to the band pass lters. Other irreversible and linear devices may be used in place of amplifiers. If desired, amplifiers may be used also on the receiving sides of the band pass lters. The outputs of the several ampliers 50 to 54, inclusive, are delivered to rectiers 55, 56, 51, 58, and 59, which are here shown as of the full-wave dry-disc type. Rectifiers 55, 5651 and 58 are each directly connected to a xed load circuit, here represented by resistances 60, 6|, 62, and 63, respectively. The resistances 60 to 63, inclusive, are connected in series with the potentiometers 68 to 1I, inclusive. The junction of each of the Xed resistors 60.to 63, inclusive, with the potentiometers 68 to 1|, inclusive, are grounded by a common lead 64. The latter also provides ground for all the rectiers 55 to 59, inclusive, through its connection to leads 'I2 and 13. The output of rectier 59 is applied to the output ends of the resistors of potentiometers 68 to 1I, inclusive, and preferably with a relay winding 65 in series therebetween. Each of the resistors '60 to 63, inclusive, is connected at its ungrounded end to a coil terminal of one of the relays 13 to r82, inclusive. The other coil terminal of each of relays 19 to 82, inclusive, is connected with a tap that is variably adjustable on one of the potentiometers 68 to' 1|, inclusive. The positive terminal of a battery 83 is applied to each of the polar relays 19 to 82, inclusive. The function lof relays 19 to 82, inclusive, is to make and break contact and to determine the direction Aof current ow in circuits energizing a plurality of servomotors A are also shown in pictorial presentation in Figs.

5 and 6. These servomotors are also arranged todrive the potentiometers 68, 69, 10, and 1| overa stationary contact 91, as shown in Fig.

5.'` The details of this construction are explained below.-

.These servomotors are electrically connected with bi-directional, polarized center-off relays 19, 80,.` 8|,and 82, respectively, and are connected in parallelwith a source of electrical energy, e. g.,.

abattery 83. The negative side of battery 83 izliereellv. @enacted .bvreason Ofihe pressure 6. of a spring 66a to a movable contact, open cir-- cuited at terminal Y in Fig. 2, of relay 66. Lead 84'connects the positive side of the battery 83 with relays 19, 80, 8|, and 82. A lead 85 connects thenegative side of the battery A88 'through relays 66 with all four servomotors 15 to 18, in-

clusive, when the relay winding 65 is energized by the passage of signal through the band pass filter 49. Any sufficient difference of potential at the coil terminals of relays 19, 80, 8| and 82 cau-ses the relay armature to close in one direction or the other to move the corresponding control accordingly. The position of the electrical null point on each potentiometer at any particular time determines the control setting that will be accomplished. To effect a change in the position of electrical null point on any of the potentiometers 68,'69, 10, or 1|, in the signal receiving station, hence, to control proportionally the missile or airplane through a. servomotor, it is necessary only to adjust one of the variable attenuators I6, I1, I8, or I8, in the signal transmitting station shown in Fig. 1, in order to vary the amplitude of the transmitted signal for the channel involved. `If an attenuator in the signal transmitting station is shifted to increase the amplitude of a certain transmitted signal, the servomotor that is controlled, as described, by that signal, will operate in such a direction as to move the contactof the potentiometer in the signal receiving station nearer to the ungrounded side of that potentiometer. Conversely, if the attenuator is readjusted to reduce the amplitude of the same transmitted signal, the servomotor will operat in the opposite direction.

In the preferred method, the several signal generators II, I2, I3, and I4 are adjusted tohave equal amplitudes of output voltage, and the modulator 28 is arranged to eiect 100 per cent modulation of the radio frequency carrier Wave when each attenuator or potentiometer 68 to -1|,- inclusive, is set for maximum amplitude of transmitted signal. The receiving system of Fig. A2 is so adjusted that the voltage across each potentiometer is at every instant equal to the volt age that would exist simultaneously across any of the load resistors 60, 6I, 62, and 63, if the corresponding attenuator in Fig. 1 were set for maximum amplitude of transmitted signal,

Additional relays such as relay 66, Fig. 2, may be incorporated in one or more of the channels to accomplish othercontrolling functions of an on-off or stepping type. Furthermore, by employing selectively any one of several standard frequencies for the constant amplitude reference signal, using relays in the relative position of relay 66 to switch the polarized relays to diierent sets of servomotors and potentiometersfor each case, it is possible to shift from one group of controls to another and thus to accomplish settings oi` many different controls in rapid succession.

Now referring to Fig. 3, this figure shows a transmitter circuit at a `control station indicated as 10| in Fig. 11.4 This station is more elaborate than that of Fig. 1 and is capable of a greater extent of control. The signal generators |00, IOI, |02, |03, |04, and I05, are like signal generators II to I5, inclusive, in Fig. 1, but the arrangement is such vthat -the first four signal generators send signals intov channels controlled by variable attenuators or potentiometers |06,-- |01, |08, and |09, or alternatively, bythe variable attenuators. or potentiometers III), III, 2, and

||f3, or by pulsing switches |22 to |25, inclusive. Signal vgenerator-s |04 and |05 send signals or pulses of' constant but differing frequencies through xed Aattenuators and ||6, respectively, and then through amplifiers |-|1 and ||8, respectively, the output from which go 'through leads v-||-9, and |20 to the terminals of a threepoint switch I2 As the circuit is shown, the output of the'signal generator |05 kis being taken, by `turning switch |2| to contact 2, the output of signal generator |04 may be taken, or fby turning the switch further to open-circuited contact 3, nc signal from either generator |04-'or |05 is taken. Switch |2| is a five-deck switch andthe resulting contacts of its separate decks are numbered identically. With switch |2| in the vnumber 1 position, variable `potentiometers |06, |01, |08, and |09 are connected. With'switch f|2| inthe number 2 position, variable potentiometers H8, ||2, and ||3 areconnected. vWith the "switch |2| in thevnumber position, no outputffrom signal generators |04 vand |85 is taken, the signals inthe first four channels are controlled by on olf keys orswitches |22, |23, |24, and |25. The rst 'four channels feed signals to -amplie'rs |26, |21, |28, |29. The fifth and sixth channelsrfeed signals to amplifiers |'|1 and ||8. All six amplie'rslare -connected-in parallel to a lead'l39. vAnother -lead 3 is "connected 'to ampliers |26, 21, |28 fand .|29 Ain nparallel, and 'to 'fthe movable f arm ofswitch |2-|. lA modulator |32 receives its input from the leads A|30 and |3|. It transmits them to a radio transmitter |33 having the usual antenna |34 and ground |35. Additional.ampli fiers may be interposed between thesignal generators and the rpotentiometer-s or attenuators if desired.

Referring 'to Fig. 4, the controlled station indicated -as 1380 in Fig. V11 has a radio receiver |36 with antenna l|31 Vand ground |38. The audio'vor super audio signal lfrom radio receiver |36 -is conducted through lleads |39 and |40 in parallel to a series Aof frequency-selective filters '|'4|, |42, |43, |44, |45, fand |46. 'which individually pass frequencies corresponding -to one of thoseoriginatinginsignal generators |00, |8|,|82,"|0'3, |04, and |05 in Fig. 3. Signal passed by the vindividual band -pass filters is conducted separately vto and then to fullWave-rectiers |53, |54, |55, |56, |51, `and |58 respectively. The vresulting signals from 'the output sides of the first four lrectifier-s, which are Yin the primary control channels of the system, are fed to the load circuits represented by lresistors y|59, |68, |6|, land |62. -On the other Ihand, outputs from yrectiii'ers |51, and |58 pass Vthrough solenoid windings |03and |64, respectively, of relays v|65 and |56, and then by means of the vlead |61, which is connected to both relay windings, the outputs are conducted to the load circuit composed of eight variable followup potentiometers |68 to |15, inclusive. The po- `tentiorne'ters are connected Vin parallel. Two of the'potentiometers are used for each of the four primary control circuits. A ground wire 'H'Bb connects all siX rectifiers |53 yto |53, inclusive,

tolground |16, -and-the battery |11 has its-posi-v tive terminal connected to Vrelay |65, while its negative terminal Lis-connectedby leads |18a, and |181) vto ground |16. A lead |19 provides fan electrical connection between'a'contact of relay |66 and a contact of relay |65. A lead I|88 is connected between each of the resistances |59, |60, IBI, and |612 and the pairs of lvariable poten- 8 tiometers |68 to |15, inclusive, and is connected by lead |182) to ground |16.

Switching'relays |8| to'l88, inclusive, 'are -connected in pairs into the `four primary 'control channels mentioned above. These switching -relays are energized in groups by battery |11 depending `upon thesettings of relays |65 and |66, as willrbe hereinafterl more fully explained. yThe switching 'relays 122| -to 224, inclusive and '324| to 244, inclusive, are ganged in pairs and 'are normally spring pressed downward.

Insofar as Fig. 4 is concerned, the groups of relays that are energized simultaneously, consist ofv four each. The groups are distinguished by their being connected to a `common contactjunc. tion marked -eitherX or I-I. AThe contact 228 of relay |65 is also marked X and the contact 23B of 'relay |66 is also marked H. Relays 1X are energized through contact 220 (X) and relays H are `energized by contact 236 (H). Relay windings lX and contact 220 are always in conjunction; likewise, relay windings H and contact 236 yare Valways joined. Switching takes place through the relays 65 and |66, respectively.

It is only due to the vcomplexity of the Fig. '4 diagram that connections rbetween the relays-X and the pointX and '-therrelays Hand the point H cannot be shown without making the vrest of the diagram -undulycomplex The letterY designatesl open circuit'ed contacts.

Polarized center-ofi' relays |89, |90, -I`9|, and |92, one for each primary control channel, Yare respectively connected by leads |93, |94, |95, and |96, Vin their respective control channels to the junctions ofthe particular rectier andthe load circuit within that channel. The other'input termin'alsof'the polarized relaysl89'to |92, inclusive, are connected by leads |91, |93, |99, and 280, respectively, to switching relays |82, |84, |86, and |88. yLeads 20| to 208., inclusive, connect'all eight switching relays with the movable contacts of Vtheeight variable potentiometers |68 to |15, inclusive. A battery 209, having its negative 'side grounded, Vis connected bye/'lead 2| 0 to the armatures of .polarized relays |89 'to |92., inclusive.

When a signaler .pulse v`passes filter |45 vand flows through the channel containingfrelay |65,

it closes relay |65 to the left againstcontact 220' and appliesthepositive potential of battery |11 to the .junction X-and energizesthe relay windings-225 to t232, inclusive. The 'energizaton of therelay windings 225 to :228, inclusive-causes the relays |8|, |83, |85, and |81 to close-toward thevleft. The energization .of the relay'windings 229, -2-30, 23|, and '232 causes the relays 222|, 222, 223,and 224 to closeiupwardly. The closing ofrelay |8| toward'the'leftcauses aisignalto pass from the tap on potentiometer |68 through therelays `|8| and |82, which are spring-pressed toward the right, -to the'lower coil -terminal on polarized frela'y |89. YIn like manner, upon the closing lof the other `relays |83, y toward the left, vthe respective channel signals are passed to vthe lower coil terminals on the polarizedrrelays-ISQ, |9i, and'l92. The'polariz'ed relays |09 to |92, inclusive, control,by means oi" |I0,y III, |l2'and `H3 controi the servomotors 2 I5, 2 I6, 2 I1 and 2|8, respectively.

' Similarly, the switching relays |8| to |86, inclusive, are controlled by relays |65 and |66 so that when a signal exists in the channel containing relay |66, the polarized relays |89, |90, |9|, and |92 are connected to the movable contacts on the respective potentiometers |69, |1|, |13, and |15, which then control the switching relays 231, 238,239, and 240. The polarized relays |89 to |92, inclusive, control, by means of battery 209, the reversible servomotors 2| 2|2, 2|3, and 2|4, respectively, which are mechanically linked, as shown in Fig. 5, to the corresponding potentiometers |69, |1I, |13, and |15. Thus, when the standard or reference signal is taken from signal generator |05 (Fig. 3) by turning switch |2| to Aposition 1, the potentiometers |06, |01, |08, and

|09 control the servomotors 2||, 2|2, 2|3 and 2 I4 respectively.

, When switch |2| is closed on position 3` (Fig. 3'), the keys |22, |23, |24 and |25 may be used to transmit one or more impulses in succession. The control system of Fig. 3 differs from that of 1 primarily in the fact that it offers control of a greater number of functions. The system of Fig. 1 incorporates a single standard signal and four separate controlling signals that are adjustable in Vamplitude at the discretion of a `pilot or operator and therefore, the system is signals, but it has two separate standard signals veither'one or neither of which maybe transmitted, depending upon the setting of transfer switch |2|. When that switch is in position l, the standardsignal from the signal generator |05 is fed to the modulator |32 and is then transmitted by the radio transmitter |33. When the switch |2| is in its position l, the controlling. po.-

tentiometers |06, |01, |08, and |09 are in the circuits of signal generators |00, 0|, |02, and |03,

respectively. When switch |2| is in its position 2, the standard signal from signal generator |04 provide ori-off control of transmission of the respective controlling signals from signal generators |00, |0I, I0?l and |03. -When switch |2| is in position 3, there is no modulation signal transmitted lfrom the system unless and until one or more of the switches |22, |23, |24 and |25 are closed by the operator.

The remotely controlled system of Fig. 4, indicated as 108 in Fig. ll, is intended for use in conjunction with the transmitting system indicated as 122 in Fig. 11 and shown in Fig. 3. In Fig. 4, the filters |4I, |42, |43, and |44 areadjusted to pass the four principal controllingY frequencies that are generated at the transmitting system. The filters |45 and |46 are adjusted to pass the two separate standard signals, either one, but not both of which may be received at any given time depending upon the setting of a certain switch at the transmitting station. There are three `separate conditions of operation to .be considered,

as follows:

a. Standard signal is being received on the frequency of filter |45, but no signal is being received on the frequency of filter |46;

b. Standard signal is being received on the frequency of filter |46, but no signal is being received on the frequency of filter |45 c. No signal isv being received on either the frequency of filter |45 or the frequency o f filter |46.

In the case (a) above, the signal passing through filter 45, after amplification and rectification, passes as direct current through the actuating coil |63 of relay |65 and thence through the follow-up potentiometers |14 and |15, which are connected in parallel to the return or ground circuit. This rectified signal current causes the relay |65 to close to the left, thus connecting battery |11 to the inner relay contact 220. Contact 220 is connected to the actuating coils 225, 226, 221, 228 229, 230, 23|, and 232 of each o f the relays I 8I; |83,.|65, |81, 22|, 222, 223, and 224, all of which are switching relays that serve to de,- termine which of the servomotors orv actuating devices will be controlled under this operating conditiony Description of the controlling operation will be limited to the control function represented by the signal frequency of filter |44 which will be seen to communicate with the polarized center-off relays |92 and the servomotor 2|4 or` v2|8 or the solenoid 254. With relay |65 closed to the left in a manner just stated,`the switching relay I 81 also closes to the left and thus connects the polarized relay |92 to follow-up potenti01neter |14. Also, the closing of relays |65 to the left, causesjthe switching relay 224 to close upwardly ,and thus connects the output terminals of relay |92 to the reversible servomotor 2|8. Thus, the followlup 'potentiometer |14 and the servomotor 2|8 which are mechanically linked together, .are controlled bythe vsignal passing the filter |44 when the standard signal through filter |45 is being used'. For the condition of standard signal at lfilter |46 and no ,signal at'iilter |45, described above in (b), there is no signal on the frequency offilter |45 and therefore the relay |65 and all other switchingrelays controlled by it are open. However, if there is a standard signal received on the frequencyl of filter |46, and that signal closes switching relay |66, the terminal H of relay contact 23,6 isconnected with the battery |11. When the relay |65 is closed toward lthe right by springr pressure and `whensignal is passed through filter |46 to energize relay winding |64,relay |66 is closed toward the left.` The positive potential of battery |11 is then appliedto the H terminal of contact 236-. The contact H is common to contact -230` and to the 'relay windings 233, 234, 235, 24|, 242, 243, 244, and 245, all of which are therefore` energized `from the positive potential of battery I 11. All contacts Y are open.

The closing of relay l| 88 connects the energizing coil of the polarized center-off relay I92to the follow-up potentiometer |15, and closing of the switching relay 240 connects the output contacts of the same relay |92 to the reversible servomotor 2|4. Thus, the follow-up potentiometer |15 and the servomotor `2|4, which are mechanically connected together, are controlled by the signal on the frequencyof filter |44 when the standard signal through filter" |46 is being used.` It will therefore be apparent that upon the simultaneous reception of signals passing filters |44 and |46, the servomotor 2 I4 may be caused to perform up potentiometers |14 or |15.

Vmechanical work such asftheadjustment of a control upon the missileor the like.

Under the conditions described above in subparagraph -(c), there is yno signal on .either the frequency of filter |45 or that oi' filter |46, and therefore the switching relays resume their spring-pressed positions with the relays |65 and |66 open cirCuited. It will be noted that in this case, the polarized, center-off relay |92 is .connected across the load resistor |62 and ground and is not associated with leither of the -follow- Also, the upper- `most .one .of the three output contacts of .relay |92 is -connected through switching relays `240 and .224 to solenoid 254. Under this condition, the relay |92 .remains `open at all times when .no .signal isbeing received on the frequency of filter |44, and the solenoid 254 is thus deenergized. However, when a signal .is received .on the frequency of the filter |44, the potential difference that is developed across the resistor |62 serves to close Vrelay v|92 in the up direction, thus connecting -battery 209 to the solenoid 254.

In this particular condition of operation, there is no proportional control feature involved be- .cause the .solenoid is either energized or deenergized, with `no intermediate conditions or positions provided.- The solenoid 254 may be used to operate any leveror other two-position devicel such as a stepping switch, valve, or other mechanism.

,Battery .209 energizes eitherthe servomotors .or the solenoids depending ,upon the position of relay 244 and the position of relay 224 and |92. The iiow of energy to these relays is controlled through filters |45 and |46. When the armature of relay. |92 is energized, the relay 244 or 240 4is connected Ato relay |92 either one way or the other. The positive terminal of battery .209 is closed upwardly and the contacts X and "H are deenergized, Then battery 209 can energize solenoid 254. When contacts X .and H are deenergized, .relay |92 cannot close downwardly. The lower coil terminal of relay |92 is grounded through the deenergized relays |81 and |88 since the polarity of the voltage applied to the upper coil terminal cannot be reversed because of the fixed manner of connection of the rectier |56. The upper coil terminal is connected with the positive terminal of load resistor |62. Relays |89 to'l92 act as one-way relays when terminals X and H are both deenergized.v For example, when X is energized and H is not energized, the lower cofil terminal of relay |92 is connected to the mov- .able contact of the potentiometers |14. The armature of relay |92 can now close in either direction. If it closes upwardly, the positive terminal .of battery 209 is connected through upper armature of relay 244 to the upper armature 224 nfrelay232 and thence to the upper power input terminal of motor 2|8. When relay |92 closes downwardly, the positive terminal of battery 209 is connected through the lower armature of relay 2-44 to the lower armature of relay 232 thence to the lower power input terminal of .motor 2|8. When terminal H is energized and terminal X is -not energized, the relay |92 acts as apolarized, center-ofi relay because its lower coil .terminal .is connected to the movable contact of potentiometer through relay |03. When .relay |92 is .closed upwardly, the positive .terminal of battery .209 is connected through the upper armature of relay 244 and thence to the upper power` vWhen .relay |92` battery 209 is connected through the lower armature of relay 244 Vto the lower power input terminal of. motor `2|4. Terminals Xand H cannot be simultaneously energized, because the standard lsignals `on the frequencies Vof vlters |45 and |45 are never transmitted simultaneously. See switch '|21 on Athe transmitter (Fig. Y6) i. It is to be .understood that the servomotors are .all provided with splitfield windings (not shown) `so tha-t, energization of one terminal will produce ythe opposite direction of rotation from that produced by energization of the other terminal.

In Fig. 4, kdue to the `complexity of the diagram, vit is impossible to show the mechanical linkages lwhich exist between .the servomotors and .the potentiometers without making the remainder Aof the diagram unduly complex. Such linkages 2| 9, and 2|4 with potentiometers |68, .|69, |10, |1|, |12, |13 |14, and |15, respectively.

Referring Anow to Figs. 5 and 6, the nature .o f the mechanical linkage between a reversible servomotor and a potentiometer is illustrated. A servomotor 15 is bolted to a gear box 94, which contains `a driving vpinion 95, which is in mesh potentiometer 68 which .is essentially a resistance coilmounted .on a .circular insulator and making Contact with a spring-pressed brush 96 .in astationaryV brush holder mounted in the floor kof the y box 94. AThe potentiometer 68 is driven by the countershaft 91a,

In this arrangement, the total angular movement of the coil of vthe potentiometer 68 is Yequal to the total angular. movement of ,the control cable reel 99. .An arrangement in which the p0- tentiometer would Vbe stationary and the contacts movable would be the full equivalent of the above combination.

Theremote control system represented bythe transmitting system .of Fig. 3 and the receiving system of Fig. 4 provides an additional group of four proportional controls for .setting the trim tabs, cowl iiaps or other auxiliary .devices on the missile, test airplane or the like. These controls must be accurately positioned, but do not require continuous attention or adjustment by the remote pilot. This particularembodiment of the invention,l which also includes the on-oi switches orkeys |22, |23, |24, and |25 which operate the solenoids 25|, 252., 253, and 254 on the controlled missile. These on-off cr step-function .controls are provided for the operation of landing-gear retraction and extension, dive-brake opening and closing, the turning on and off of cameras or other special devices on the missile or airplane, .and for .any other functions that have onlytwo positions or conditions of operation.

`In the preferred manner of application, one oi 'the solenoids on the missile is used to .actuate a chain of lock-in relays ora. steppingy switch of the type commonly, employed in automatic telephone exchanges; .another solenoid is used to reset the relay chain or stepping switch .to the home position; a third solenoid is used to energize the lparticular step function selected in the positive direction and the remainingsolenoid is used to operate the selected step function 13 'in the negative direction. To illustrate the mannerof use of this feature of the total control system, let it be supposed that on a particular installation, the landing-gear retracting mechanism is connected to the third position of the relaychain or stepping-switch. To actuate the landing gear retracting mechanism, the remote pilot Will close and open three times the stepping switch that controls the first solenoid on the .missile or aircraft and will thereby advance therelay chain or stepping switch to its third position. If he then desires to retract the landing igear, he will close the actuating switch that controls the third solenoid on the missile or airplane. Such closing will cause positive direction of operation of the selected step function:

Qn the other hand, if he desires to lower the landing gear, he will close the actuating switch :furthe fourth solenoid. Such closing will accomplish negative direction of operation of the selected step-function. After completion of the desired operation, the remote pilot will close his second step-function switch, thereby energizing the second solenoid on the airplane and returning the relay chain or stepping switch to its home position. A step function system of the type just described, incorporating four on-off switches or two double-throw switches at the'remote control transmitting station and four cooperating solenoids on the remotely controlled airplane may be used to control as many separate step functions as desired. The number of such functions available for control is limited only by the number of discrete steps in the 1 .relay chain or the stepping switch on the test airplane.

It will be seen that the transmitting system of Fig. 3 is capable of controlling selectively two separate groups of four each proportional controls and one set of four each on-ofi` or stepping controls. There are two diierent ways -in which the transfer switch I2I can be utilized which are as follows:

a. v It can be manually set by the controlling pilot, who would thus select the particular group of functions desired to be controlled at any time, or;

. b. The `form shown in Fig. 3a can be continuously and automatically driven through its several positions by a motor or other continuously-acting device, thus to provide automatic sampling of each of the separate control groups at regular intervals.

With rapid action of the switch I2I, the systemffcan be made to display for all particular purposes, continuous availability of all twelve of the separate control operations. The switch may be mechanically actuated in the manner just mentioned or it may consist as an equivalent of a wholly electronicdevice in which electronic gates are opened and closed in predetermined sequence by a controlling oscillator or pulse generator.

Referring now to Fig. 3a, the switch I ZI may comprise in each one of its decks a plate-like circulti I 2Ib which is made from an insulating material such as a plate of synthetic resin. Mounted centrally therein for rotation is a shaft I2Ia which may be driven by a separate electric motor, y

mounted upon the base plate I2Ib. Lead `I`20 connects with segment I2Id;`lead I3I connects y with the shaft end of the movable arm I 2Ic and lead IIB connects with the segment I2Ie.

to either side of the geometrica] center of the potentiometer; and

b. Control position indicators on the missile i by which the pilot or operator can determine at any time the control position that is being called for by the transmitting system in each of its separate channels.

As in the other transmitting systems previously described, the present arrangement employs five signal generators II', I2', I3', and I5' which are identified in Fig. 1 as II, I2, I3, I4, and I5. Each of these signal generators produces a constant frequency and constant amplitude of output, but no two of the frequencies are the same. The signal generators II' to I4', inclusive, as in the previous showings, apply their outputs to variable potentiometers I6' to I9', inclusive. The signal generator I5' which delivers its output to a constant load resistor 300, produces the standard or reference signal for the system shown in Fig. 7. This signal passes through the amplifier and filter combination 21', thence into the modulator 28', the radio transmitter 3|', and isradiated from the antenna 32'. The signal generator I4', which produces another signal, delivers its output to the network consisting Aof potentiometer I9', resistor 30| and potentiometer 302. The potentiometer 302 is the control element by means of which an operator can obtain at the frequency of generator I4', a signal having an amplitude from zero to the full output of the signal generator. The potentiometer I-9' in conjunction with the resistor 30| constitutes the trim adjustment which will be explained later. The output signal from potentiometer 302 passes to a filter and. amplifier unit 23' and thence to the same modulator 28. transmitter 3|' and antenna 32'.

.The other channels following signal generators II', I2 and I3' are similar to that of I4' except in the matter of frequency. 4'I'hey operate in the same manner to produce control signals that can be separated and individually used at the receiving station. The control po'- sition indicators 303, 3M, 305, and 306 are zero center, direct-current instruments observable by the pilot at the remote control transmitting station. These instruments are employed in differential vacuum tube voltmeter` circuits to measure the relationships between the standard signal amplitude and the adjusted amplitudes of each of the other control signals. -z The action of the trim-'adjustment potentiometer will be explained with reference to the channelof signal generator Id. The resistance elem-ent of the trim-adjustment potentiometer I9' connected in parallel with the control potentiometer 302. One end of the range resistor 30| is connected to a center tap on the potentiometer '3.02 and the other endl of this resistor is connected to the movable contact on potentiometer I To examine the operation of this trim-control adjustment, the case in which the movable contact on potentiometer I9' is in the center of that potentiometer, will be first considered. In such case, both ends of the yresistor 30| are always at a potential midway between ground and the output potential of the signal generator I4. Hence, there is no potential difference across resistor 30| and no current iiows through it. Un- .der this condition, the presence of potentiometer I9 and resistor 30| has no effect on the control potentiometer 302 and the latter potentiometer maintains linear relationship vbetween geometrical setting and output voltage.

However, if the movable contact on potentiometer I9 is moved tothe top position possible in Fig. 7, it will be noted that the resistor 30| is in shunt with the upper half of potentiometer 302. In this condition, the geometrical center of potentiometer 302 is at an electrical potentia-l greater than one half of the total potential output of the signal generator I4. This maximum setting of potentiometer I9' produces therefore, an electrical center point on potentiometer 302 that is somewhat below the geometrical center of that potentiometer. On the other hand, if the movable contact on potentiometer I9 is placed at the lower end of that potentiometer, then the resistor 30| is in shunt with the lower half of the control potentiometer and thus moves the electrical center of potentiometer 302 abo-ve its geometric-a1 center.

When the movable contact on the potentiometer I0 is at any other position than its center or upper or lower limits, the effect is to place unequal shunting resistan-ces across the upper and lower halves of 'the control potentiometer 302. Thus, the combination of potentiometer I9 and resistor 30| provides f0.1' unsymmetrical shunting of the two halves of potentiometer 302, in -either sense about the symmetrical condition and thereby furnishes a trim control for the flight controi element on the controlled airplane ogr missile that is actuated by the channel origihating in signal generator I4'.

Four separate control position indicator circuits are shown in the lower part of kthe diagram of Fig. 7. Since all of these indicator circuits are substantially identical, the numerals designating the parts of the other three indicator circuits are the same as those of the first except that they are followed by the letters a, b, and c, respectively. The following explanation will therefore be applied only to the first circuit at the left of Fig. 7. That circuit comprises the indicating meter 303, the vacuum tubes 324 and 3125, and associated circuit elements. Th-ese vacuum tubes are used in a differential cathode-fo-llower arrangement with each tube initially biased to plate current cut-off so as to produce half-wave rectification of the incoming grid signal. This effect is accomplished by inserting in the cathode circuits comparatively high resistances 326 and Y321 to prod-ucc essentially full cathode-follower action in the vacuum tubes 324 and 325 and, by initial adjustment of the potentials of the batteries 308 and 309 to produce plate current cut-off in the respective vacuum tubes. The indicating meter 303 is connected across the shunt resistors 3I0 and 3| I, each of which is in the cathode circuit of one of the vacuum tubes. The lter condensers 3| 2 and 3I3 may be connected across the shunting resisters as shown, to smooth pulsations of meter current that otherwise would be caused by lthe half-wave action of the plate currents in the vacuum tubes. It will be noted that signal voltage from the standard frequency generator l5' is fed through a blocking condenser 3I4 to t-he potentiometer 3I5 which i's in -the grid circuit of the vacuum tube 324. Similarly, the adjusted output voltage of potentiometer 302, which is in the control circuit of the signal generator I4', is fed through its blocking condenser 316 to the potentiometer 3 I 'I in the grid circuit of tube 325.

To illustrate the manner in which the control position indicator 303 is used, let it be assumed that the potentiometer 302 is first placed at the lower limit of its travel, thus delivering zero signal at the frequency of signal generator I4'. Then, as the signal generator |4 has been adjusted to its normal voltage output, the potentiometer 3I5 is adjusted to a point which 4gives sufficient grid signal to tube 326|r to produce fullscale deflection of the meter 303. Next, the control potentiometer 302 is moved to its top position, thus delivering maximum signal output at the frequency of signal generator I4. The potentiometer 3I'I is adjusted to such a point that the indicating meter shows full-scale deflection in the direction opposite to that produced above. After adjustments have been made in this manner, the indicating meter 303 will show deflections which are at all times indicative of the electrical position of the control potentiometer 302. For example, when the potentiometer302 is set to its electrical center position, the meter 303 will stand at its zero center, thus indicating that the control channel represented by the signal generator I4' is set to produce neutral or center position of the rudder or other controlled elem-ent at a remotely-situated receiving stati-on. The main channels as represented by meters 303, 304, 305, and 306 therefore furnish a complete presentation to the pilot of the position settings being called for by the transmitter station for the ight controls of the missile or airplane.

The schematic diagram of Fig. 8 shows a complete radio-controlled receiving station of the general type that has been previously described, but incorporating certain additions and modifications not before illustrated. For simplicity, the diagram shown on Fig. 8 includes only two channels for control. It is to be understood that four or more signal channels, besides the standard or reference channel, generally are to be used. Among the more important new features indicated on this diagram are the following:

a. The follow-up potentiometers 40| and 402 substantially correspond to the follow-up potentio-meters 68 to 1I, inclusive, in Fig. 2, but 40| and 402 are connected in alternating current cir- -cuits ahead of the rectiers 4II to 4I4, inclusive, in Fig. 8, rather than in the direct current circuits following the rectiers 55 to 59, inclusive, 'as are potentiometers 68 to 1I, inclusive in Fig. 2;

b. Thermionic full-wave rectication is used instead of the dry-disc type shown in Figs. 2, 4, and l0;

c. Gas-lled electronic tubes are used as sensitive relay devices;

d. A hydraulic servo system is shown in place of the electric motor servos indicatedinrthepreceding gures;

e. An anticipating or anti-hunting circuitis included; f

f. The system includes a throw-out switch b y which a human pilot or operator can `quickly 17 throw the complete remote control system into or out of operation; and

g. Signal lamps are provided to indicate to a human check pilot when the transmitter station is calling for control settings different from those i existing on the controlled airplane or missile.

Major subdivisions of the control-receiving system of Fig. 8 will be mentioned briefly and will be followed by detailed description of one of the two channels shown. ates in a similar manner.

The antenna 40 receives a modulated radio Wave from any one of the transmitting stations shown in the drawings. The receiver 41' demodulates the radio wave and delivers the combined modulation frequencies to the inputs of the three filters 45', 46', and 47', which are connected in parallel. These lters are of the band-pass type and are individually adjusted to pass the frequencies corresponding to outputs of signal gen erators i3, 14, and at the transmitting station (Fig. 7). The output of filter 4'1, which is the standard or reference signal, is applied across the two follow-up potentiometers 401 and 402 which are in parallel. low-up potentiometer 402 is applied through an ampliiier 403 to the primary winding of the transformer 404 and the output of the other follow-up potentiometer 401 is similarly connected to its transformer 405 through ampliiierfv The output of the filter 46 is connected directly through the ampliiier 40'1 to the primary winding of the transformer 408 and the output of the filter 45 is similarly applied through ampli-'.

er 40S to the primary winding of its transformer 410. The secondary winding of each of the transformers 410, 4135, 408, and 404 is connected to a vacuum tube 411, 412, 413, or 414, respectively, in a conventional full-wave rectification'.

circuit that includes a xed load resistor 415, 416, 4i?, or 4i8. These rectiiication circuits are grouped in pairs, one variable-amplitude control channel being paired with one reference channel, and the two load resistors of each pair (for example 415, and 415) are connected in polarity opposition across a resistive network 419, 420 having its midpoint grounded. Gas-filled elecronic tubes 421, 422, 423, and 424 have their control grids connected to the resistive networkY on opposite sides of its neutral or ground point, and these tubes are thus diierentially controlled 'by the rectied signals. In the plate circuit of ieach of the gas-filled electronic tubes is a relay winding 425, 425, 427, and 428 which closes all `corresponding relay switch 480', 480, 431', and I481, respectively, when the associated one of the above tubes is rendered conducting by an increment of positive signal applied to its grid. One contact Y of each of these relays 480, 480', 481 .and 451', is an open contact. Each of the relays 435' or 481', when closed downwardly and relays A480 and 481, when closed upwardly, energizes a winding and thus opens one or more solenoidoperated hydraulic valves 429 to 438, inclusive, which control the motion of hydraulic servos 438, 44E. Finally, each one of the hydraulic servos 439 and 445i is connected by some suitable mechanical linkage such as a flexible cable and pulley arrangement (not shown) to the rudder (not shown) or to some other controlled element on the missile or airplane.

For a more detailed analysis of the operation of this remote control system, the channel repre- 4sented by filter 46 leading to the hydraulic servo The other channel oper-` The output of the fol,

f relays 480', 480, 481 and 401 are therefore open when no controlling signals are being received through the iilters 4l', 45', and 45. Positive bias applied to each such cathode should be only slightly greater than that required to render the tube nonconducting, so that tube conductivity can be achieved by application of a small increment of positive grid signal, After this initial adjustment has been iii-ade, the system is ready for operation and the receiver may be switched on.

The standard signal is received through the filter 41 at a fixed'and constant amplitude, and the controlling signal is received through its iilter 46 at an amplitude which may be varied at the transmitting station by the potentiometer 302 of Fig. 7. Let it be assumed that the amplitude of the controlling signal through 45 is set at maximum and is equal to the total amplitude of signal through the reference channel 41'. Let it also be assumed that the controlling potentiometer 302 on Fig. 7 is set at its midpoint. The incoming signal through amplier 401 is rectied by the tube 413 and is thus converted into a D. C. potential across the load resistor 415 with the polarity as shown. Similarly, the other signal through amplier 403 'is rectified by the tube 414 and appears as a direct potential across the load resistor 415. In this case, the voltage across resistor 416 is twice that across resistor 415 because of the assumed setting of the potentiometer 302.

Since the resistors 415 and 416 are effectively connected in parallel, a current will flow through the resistive network 419 comprising resistors 449, 450, 451, and 452, and the direction of this current ow will be such as to make the top of resistor 452 positive with respect to ground and the bottom of resistor 450 negative with respect to ground. The resistor 451 and condenser 453 serve as a lter to produce essentially pure D. C. through the resistor 452 and the resistor 449 with condenser 454 serves the same purpose with respect to resistor 450. The negative potential at the bottom of resistor 450 is applied through the resistor 463 to the control grid of tube 421 and thus provides additional bias on this tube in the direction of nonconductance. On the other hand, the positive potential at the top of the resistor 452 is applied through resistor 455 to the control grid of tube 422 and produces an eiect opposite to that of the initially-applied positive cathode bias and serves to render tube 422 conductive when positive half-cycles of plate voltage are applied through the transformer 442.

The resistor 455 is introduced into the grid circuit of tube 422 to limit grid current to a negligible value during conducting half-cycles in that tube. Rendering the tube 422 conductive results in the closing upwardly of relay 480 which thereby energizes and opens solenoid-operated valves 429 and 432. -A resistor 456 in the plate circuit of tube 422 serves to limit maximum plate current through that tube to a safe value. Open- 19 ing of the valve 429 admits hydraulic fluid to the bottom of the servo 439, and the simultaneous opening of valve 432 connects the .top of the same servo to the hydraulic reservoir.

This sequence of revents causes the servo 439 to move the servo piston rod 451 in a direction to produce a desired result such as downmotion of a control element on the missile or airplane.

The foregoing description shows how the servo is caused to move and the direction of that motion. The next matter to be considered is how far the servo will move and under what conditions it will assume a fixed position. The follow-up potentiometer 402 is mechanically connected to the movable piston of the servo 43S as indicated by a dashed line y482 in such a manner that these two elements move together and have coincident limits of travel. The mechanical linkages 482 and 483 connect the hydrauiic pistons 451 and 484, with their follow-up potentiometers 402 and 40|, respectively. Recalling that a servo motion was initially produced because the signal through amplifier 401 was greater than that through amplifier 403, it will be seen that movement of the-potentiometer 402 toward its upper `limit will increase the signal through amplifier 403 and thus tend to establish vequality of the voltages developed across load resistors 4l5 and 416.

Since the signals ythrough lters 40 and 41 were assumed to be equal, it is apparent that the signal through amplifier 403 will be equal to that through amplifier 401 when the potentiometer 402 is at its extreme upper position. Placement of potentiometer 402 in its extreme upper position produces equality of voltage across resistors 4I5 and 416, reduces to zero the current through resistors 450 and 452 -and thus removes all grid signals from the gas-filled electronic tubes 42! and 422. When this ycondition is reached, relay 480 remains open, relay 430 opens, thus closing solenoid-operated valves 429, and 432, and the servo 439 is stopped and hydraulically locked in position. Therefore, prop-er mechanical linkage between the servo 430 and the follow-up potentiometer 402 'is that in which the maximum down position of 'the control element on the airplane corresponds to the maximum up position of the potentiometer 402. Similarly, the maximum up position of the control element on the airplane should correspond to the maximum down position of the potentiometer 402. With the follow-up potentiometer connected in this manner, servo motion always moves the follow-up potentiometer in a direction tending to establish equality of signals through amplifiers 403 and 401. Servo motion stops when that equality is established. The system automatically adjusts a follow-up potentiometer 402 to pick off a definite fraction of the standard signal through filter 41 and that fraction is equal to the amplitude -ratio of signals sent through the amplifier elements 25' and 21 of the transmitting system in Fig. 7.

To illustrate the opposite direction of servo motion, it is convenient toconsider the condition in which the lcontrolled 'element on the airplane is in its full down position and the `follow-up potentiometer 402 is in its 'full up position. If the controls at the transmitting station are then manipulated in such a manner that the `amplitude of signal through lter 40 of Fig. 8 is reduced to one half of its former (maximum) tvalue, the rvoltage developed across resistor 4|5 will be twice that developed across .standard signal vthrough lter 41.

Z0 .resistor M6. Thebottomof resistor 450 will be positive with respect to ground and the top of resistor v452 will be negative with respect to ground. This ysituation causes the tube 15:2! to :become conducting, closes the relay 480 downwardly, .opens the ,solenoid-operated valves 430,

-43 l, introduces hydraulic pressure into the upper end of the servo 439, connects the lower end of the .servo to the Ihydraulic reservoir and thus lcauses the controlled element on the airplane to move upward from its full down position. .It is evident that equality of signals through ampliers 403 -and 401 will be established, hence, .servo motion .will be stopped when the follow-up potentiometer v402 reaches its midpoint because it will .then `be picking ofi 50 per cent of the Therefore, the 'controlled element on the airplane will come to rest in its center or neutral position. The

`dashed lines 482 Aand 483 `which bear the legend Mechanical linkage indicate a drive for the potentiometers similar to that illustrated and described in relation to Figs. 5 and 6.

In regard to the biasing system empioyed for the gas-filled electronic tubes 421 and 422, particularly with reference to the anticipating or anti-hunting circuit referred to previously as modification (e) contained in Fig. 8, the operation is as follows: Bias voltage is supplied by the battery 412 through the voltage-dividing circuits consisting of resistor 450, resistor 450, potentiometer `446 and resistor 464 for tube 22. The circuit just mentioned is used to provide constant but adjustable cathode bias to these tubes. It' will be noted that the resistor 450 is common to both of the cathode biasing circuits and is also connected through resistors 46E and 466 to the relay contacts adjacent the relay windings 425 and 426,respectively. When either relay winding 425 or 425 is energized, the positive terminal of battery 458 is connected through resistor 465 or-466 to the resistor 459 at its junction with resistors 462, and 400. The closure of relay 480 .or 480 produces from battery 45S an increment of current in addition to that from battery 412 through resistor 459 because the battery 458 and resistor 459 have a common ground connection at their negative ends, and thereby apply an additional increment of positive bias lto the cathodes of both tubes 42l and The effect of this action is to bias both of 'these tubes 42| and 422 farther in the direction of nonconductance, thus requiring a greater amount of positive grid signal to maintain relay closure. It must be understood that after a relay has closed and a servomotor has started to move its follow-up potentiometer, there is a small but unavoidable delay between the attainment of equal signals in ampliers 403 and 401 and the lactual'stoppage of servo motion. This delay is due to time constants of the various parts of the electrical circuit, to the time required for relay opening, ito the time required for the solenoid-operated valves to close and perhaps to other factors.

The practical result is that if no anticipating circuit were provided, the follow-up potentiometer 402 would be driven past its proper balance point before the balance condition could exert its effects to stop the servo. Such overshooting could produce errors in the iinal resting point of the controlled element on the airplane, and, if serious, would result in continuous oscillation of the controlled element. With the anticipating or anti-hunting circuit in operation, however, the

cathode bias and grid bias conditions on the gaslled electronic tube necessary for relay opening are established before the follow-up potentiometer 402 has reached its electrical balance position. Values of resistors 459, 465, and 466 can be chosen so that, with a given voltage of the battery 458, a proper amount of anticipation will be obtained for any given speed of servo movement. In any given installation, servo operating speed does not ordinarily change after having been initially set to a suitable value. The polarity of the increment of cathode bias applied by this anticipating circuit is the same regardless of the direc tion of servo motion.

A switch 461 which is an eight-pole, doublethrow switch, the arms of which are ganged as shown by the dashed line 485, isprovided as an illustration of the modication (f) included in Fig. 8. By the use of the switch 461, the entire remote control system may be thrown in or out of operation at the discretion of a human pilot in the remotely controllable airplane. When the switch is closed downwardly as shown in Fig. 8, the remote control system is fully engaged and operable as described above. However, when this switch is closed upwardly, the servo-actuating valves 420, 430, 43|, and 432 are disconnected from their ground-return circuit to the battery 458 and therefore cannot be operated by closure of their associated relays 480', 480, 48| and 48|.

Also, closing of the switch 461 upwardly energizes and thereby opens the solenoid-operated valve 433 which serves to by-pass and hence 'to unlock hydraulically the servo 439. The closing upwardly of switch 461 renders the remote-control system ineffective and at the same time frees the hydraulic servo system so that the controls on the airplane can be manually operated by a human pilot in the conventional manner.

Signal lamps 468, 460, 410, and 41| are provided, two in each channel of the remote control system to indicate to a human check pilot in the remotely controllable airplane when the remote control system produces relay closure of any of the relays 480 or 48| upwardly or 480 or 48|' downwardly and thereby calls for servo motion. The signal lamp 410 is energized by the closure downwardly of relay 480 and hence shows when the remote-control system is calling for up motion of a control element on the airplane. a'

Similarly, the signal lamp 41|, which is energized by the closure of relay 480, shows when the remote control system is calling for down motion of the same control element on the airplane. When the system is operating properly, it is impossible for both signal lamps of any given pair to be turned on at the same time. In a similar manner, a closing upwardly of relay 48| applies the potential of battery 458 across vthe filament of lamp 468 and when the relay 48| is closed downwardly, the potential of battery 458 is applied across the lament of lamp 460.

The chief practical use of the signal lamp system is to indicate to a human check pilot in the controlled plane when he may safely switch over from manual to remote control. For example, if an airplane has been taken aloft by conventional manual control and if it is then desired to switch over to remote control from a groundbased or airborne transmitter station, it is desirable that the controlling potentiometers at the transmitting station be set in positions correspending to the actual positions of the controlled velements on the airplane before the changeover is made. If this condition were not satisfied.

more or less violent reactions of the airplane would result when the airplane controls adjusted themselves to the settings dened by the transmitting station. Therefore, the normal procedure is for the human check pilot on the controlled airplane to instruct the pilot at the control station through radio communication to readjust his transmitting controls so that all signal lamps on the controlled airplane are off, indicating that all controls are set as required by the transmitter station. When that condition is attained, it signifies that the remote control system is not calling for any change of servo position on 'the controlled airplane and therefore, no immediate change of airplane attitude will result from a switch-over from manual to full remote control. The various signal lamps used are preferably of distinctive colors and are so-placed and identified that the check pilot on the controlled airplane can tell at a glance which controls are being energized by the remote control system and the direction of motion that is being called for in each case. All signal lamps are fully operative regardless of the position of the switch 461.

Fig. 9 is a diagram of a remote control transmitting system that is similar to Fig. 1 except for the means by which the combined controlling signals are radiated into space. The relationship between Figs. l and 9 is indicated by corresponding numerals with the letter d added. In Fig. 1, the several controlling signals were combined and then were radiated as modulation on a radio frequency carrier wave, whereas in Fig. 9 the combined controlling signals are amplified and then applied to a generator of light, such as a gaseous glow-discharge tube 500, and are then transmitted through an optical system 50| as modulation on a light beam 502. In the system of Fig. 9, the several signal generators, controlling potentiometers, and isolating amplifiers, and the combined modulation amplifier l563 operate in substantially the same manner described in connection with Fig. l.

The combined signals at the output of the amplier 503 are fed through the blocking condenser 504 to the control grid of the vacuum tube 506. The cathode resistor 501 in the circuit of the Vacuum tube 506 is provided in the usual manner to generate appropriate cathode bias for operation of that vacuum tube on the linear portion of its characteristic curve, and the by-pass condenser 508 is connected across resistor 501 to provide a low-impedance path for the dynamic components of cathode current. The resistor 509 is connected in the conventional manner to provide a direct current return circuit from the control grid to ground. A battery 5|() provides, through the tube 500, cathode-to-plate potential difference for the vacuum tube 50S in the usual manner. The gaseous glow-discharge tube 500, which may be a neon tube, is inserted in the plate circuit of the vacuum tube 506 in a manner such that the plate current flows through the discharge tube 500 and thus generates light rays whenever the vacuum tube 506 is conducting. The gaseous glow-discharge tube 506 should be one in which the intensity of the generated light is proportional to the electric current passing vthrough that tube.

To illustrate the operation of this transmitting system, let it be assumed first that the cathode heater (not shown) of the vacuum tube 506 is fully energized, and that no grid signal is being impressed through the condenser 564. In this condition, the value of resistor 501 should be adjusted so that the grid bias withA respect; to cathode is midway between zero and the vmaxi'- mum negative value for linear variation with plate current. Under this condition, the plate current on vacuum tube M will be set at its normal value, and thev intensity of light emitted oy the gaseous-glow-discharge tube 55d will be midway between its maximum and minimum values. Now, if the signal generators, amplifiers, and all other parts of the circuit are placed in operation, a composite alternating voltage wave containing, in general, ve different frequency components originating in theve separate signal generators, will be transmitted through the condenser 50/3 to the control grid of the vacuum tube 06. Due to the well known plate-current-versusgrid-voltage characteristicsof a vacuum tube such as '53%, the current through the gaseous-glow-discharge tube will vary in accordance with the instantaneous values of. signal voltage appliedV to the control grid and willv thus produce changes of intensity of light radiated fromv the discharge tube :5i-d. Positive increments of signal voltage applied to the control grid or vacuum tube 56S will cause increases of the plate current and hence, increases of light intensity from the gaseous-glowdischarge tube 5ml. Similarly, negative increments of signal voltage appliedv to the control grid of vacuum tube 5% will decrease the intensity of light trom the glow-discharge tube 5&9.

Under the stated conditions in which plate current in the vacuum tube 56d is a linear function of applied grid voltage and in which intensity of radiated light from the gaseous-glow-discharge tube 59] is a linear function of the current conducted through that tube, the radiated light intensty will be a time function corresponding to the composite voltage signal wave applied to the control grid of vacuum tube :'l. A suitable optical system 5M, here represented by a converging lens, may be employed to direct the modulated light in a beam of essentially parallel rays for maximum eiective distance of transmission and for maximum security against unwanted interception. Modulation of the light beam 502 so produced, is used to eiect control of the missile or airplane.

Fig. 1G is a diagram of a circuit at the receiving station by means of which the modulated light beam from the transmitting system of Fig. 9 may be intercepted and converted into electrical signais which, in turn, may be separated and channeled to individual servomotors or other control actuating devices on the missile or controlled airpiane. ln the circuit of Fig. 10, the relationship between it and Fig. 2 is indicated by corresponding numerals with the letter d added.y A Converging lens 665 focuses the received light beam 555@ upon the, cathode surface of a photo-electric cell EUG, which is here shown as a high-resistance, emissive type. Potential diierence across the photo-electric cell cil@ is maintained by the battery im! which is connected in series with the load resistance S52. Incident light upon the cathode of the photo-electric cell 680 causes current to flow through thek circuit just mentioned, and thus produces voltage drop across the resistor 602. The characteristics oi the photo-electric cell employed should be such that changes of intensity of the incident light will produce proportional changes of potential drop across the load resistor 632. Under these conditions, the dynamic component of potential d-iierence across the resistor 882 will be a reproduction of the modulationsignal applied to the light beam at the transmitting station. This reproducedV signalmay be transferred through the. blocking condenser @i3-3, the preamplier 6M tothe same filter circuits and subsequent circuits; previously described in connection with Fig. 2^. Such circuits govern the servomotors 15d to 18d, inclusive, in the manner previously'described, for the purpose of actuating the controls on the missile or controlled airplane.

Fig. 11 has previously been described as an overall presentation of the remote control system disclosed herein.

Modications may be made in the circuits and combinations disclosed herein without departing from the spirit o1 the invention, for example, the carrier wave transmitter or equivalent andthe carrier wave receiver or equivalent may be eliminated from the combination. A wire connection would in such case run directly from the transmitter station to the receiver Station and combine the transmitter and receiver to serve as a wired remote control system. Such a wire connection could be shown by a line connecting the output of amplifier 5M of Fig. 9 with the input to preamplifier SM of Fig. 10. For such use, the elements which would in the absence of the wire radiate and receive the carrier wave could then be eliminated.

The invention claimed is:

l. 1n a transmitting system for the remote control of missiles, a generator of reference signal having output leads, a plurality of generators of control signal, each of said generators having output leads and producing an output Wave of constant frequency and constant amplitude, no two requencies being the same, a constant load resistor connected across the output leads of the reference signal generator, a iirst potentiometer a second potentiometer for each control signal generator, each potentiometer being connected across the output leads of its generator of control signal, a resistor connected between a movable tap on each rst potentiometer and a nxed tap on the respective second potentiometer, the variable tap on the first potentiometer constituting means to provide for unsymrnetric shunting of the halves of the second potentiometer whereby to make the electrical center of the second potentiometer differ from its geometrical center in order to produce a trim control for the controlled missile, a mixing circuit connected to the output terminals of said second potentiometer for each control signal generator and to said load resistor, means under the control of an operator whereby the secondr potentiometer may be actuated to vary from zero to maximum that fraction of the output oi its signal generator intended for delivery to the mix-ing circuit, a modulator connected to the mixing circuit', and a radio transmitter coupled to the modulator and to an antenna.

2. A control signal transmitting system ,adaptedv for the radio guidance of a missile or a guidable airplane provided with a control- `actuating receiver adapted to receive and be actuated by signals fromv said control signal transmitting system, said system comprising a plurality of single-frequency signal generators to produce a graduated set of frequencies, each generator having, output leads, a fixed load resistor, one of said generators being connected by its leads directly to said xed load resistor to provide a reference signal, at least one of the re.-

4maining signal generators having a iirst potentiometer and. a second potentiometer connected across its output leads,v a xed tap on the windingv of saidr second potentiometer at substantially the geometrical mid-point thereof, a variable tap on the rst potentiometer connected to said fixed tap on the second potentiometer, said variable tap being under the control of an operator for varying the setting of the rst potentiometer between maximum and minimum to provide for unsymmetric-al shunting of the second potentiometer, whereby to make the electrical center of the second potentiometer different from its geometrical center in order to producev a trim control for said guidable missile or airplane, a mixing circuit connected to the output sides of the second potentiometers, a modulator connected to the mixing circuit, and a radio transmitter coupled to the modulator and to an antenna.

PAUL W. NOSKER.

REFERENCES CITED UNITED STATES PATENTS Number Name Date 2,184,075 Goldstein Dec. 19, 1939 2,382,709 Greene et al Aug. 14, 1945 10 2,385,657 Stettler Sept. 25, 1945 2,388,748 Kopetzky Nov. 13, 1945 2,397,475 Dinga, Apr. 2, 1946 2,397,477 Kellogg Apr. 2, 1946 2,441,568 Finison May 18, 1948 15 2,490,844 Sorensen Dec. 13, 1949 

